Network configuration and optimization are time consuming and complex tasks. In a large network with a huge or extensive number of small cells, the process of determining the right or most appropriate neighbor to include in the neighbor lists that are used to configure the network is a substantial task. Therefore, It is desirable that at least a part of it could be made as automatic as possible. Various methods for making these tasks as automatic as possible are proposed in reports: R2-061545, Complexity minimization to setup and optimize an LTE network, T-Mobile, KPN; R2-061929, Standardization policy for plug and play RAN, NTT DoCoMo; R2-062230, Discussion on Auto-configuration and Dynamic Optimization, Lucent, T-Mobile; R2-062156, Measurements for Network Optimization, Motorola, T-Mobile; R2-062411, Support for self-configuration and self-optimization Proposal for Stage2, T-Mobile; R2-062940, Support for self-configuration and self-optimization Proposal for Stage2 (only RAN2 relevant part), T-Mobile. and which reports are fully incorporated herein by reference.
As it is only the terminal itself, which can accurately know what cells it is able to detect in a certain location, it is expected that the search of new neighbor cells is an area where UE support for network configuration and optimization is needed. Thus, one of the UE tasks to support network self-configuration and optimization is the search of neighbor cells outside the current neighbor list of the serving cell.
Normal user equipment (UE) can be used to assist network self-configuration and self-optimization if the UE is able carry out measurements on the serving cell, the neighbor cells and the search of neighbor cells outside the current neighbor list. One way to do this is to signal all the mobile terminals to measure all theoretically possible neighbors. This solution can be implemented by sending separate measurement commands to the mobile terminals or by adding the potential neighbors in the cell's neighbor list. This is a relatively simple method to get measurement data from the mobile terminals that are in various parts of the cell. In the long run, the data will show which cells are the ones that have a sufficient strength in at least some parts of the serving cell and thus should be included in the neighbor list. This approach requires a substantial measurement time period to guarantee that the entire serving cell area has been covered by the measurement data.
However, even if the extra measurements are limited to situations where the network setup has been changed (new or modified cells), continuous search, particularly of neighbor cells outside the neighbor list, will use the UE resources, most notably the battery power more than the normal neighbor cell measurements that are used for supporting handover or cell reselection evaluation.
Furthermore, this type of blind neighbor cell searches may also degrade the performance of normal neighbor cell measurements used for handover and cell reselection purposes. If the network is allowed to use the UE measurement capability for supporting network self-configuration and optimization continuously without any limitations, it is likely to have an unacceptable negative impact on user experience of terminal performance and in some scenarios on system performance as well. Because the number of measurements needed to get a statistically sufficient amount of data for the network configuration and optimization may be huge, and because it is difficult to guarantee that also the rarely used areas within the cell have been visited by at least a few mobile devices, it is important to limit the amount or numbers of the UE measurements used for network self-configuration and optimization purposes to an acceptable level in each UE. Also, because the mobile terminals carrying out the measurements move freely within the serving cell, it is impossible to know when all the places or locations in the cell have been visited by at least some mobile terminals in such a mode where measurements are possible. Usually, the mode where measurements are possible means a mobile terminal with an active connection, however, mobile terminals in the idle mode may also be used to determine neighbors in the neighbor list. Further, the extended measurements are kept active for a substantial time interval and the extra power consumption by the mobile terminals that is used in making the extended measurements for the neighbor list determination will more quickly deplete the battery charge. The faster battery discharge will in all likelihood lead to user dissatisfaction.
What is needed is a way to limit to an acceptable level the negative impacts on a UE caused by the UE's support in network self-configuration and optimization.